The present invention relates to a an airbag module to be installed in a vehicle and, more particularly, to an airbag module having a horn switch.
Airbag modules for protecting an occupant in a driver's seat of a vehicle (hereinafter, referred to as “driver-side airbag module”) include a retainer (sometimes, referred to as “container”), an airbag of which base end side is fixed to the retainer, and a module cover which is attached to the retainer to cover the folded airbag. In addition, an inflator (gas generator) for generating gas to inflate the airbag is normally fixed to the retainer. As the inflator generates gas in the event of vehicle collision or the like, the module cover is torn and the airbag deploys in front of the occupant in the driver's seat.
The module cover is provided with tear lines (sometimes, referred to as “thin-wall portion” or “easy-to-break portion”). The module cover is torn along the tear lines when the rear surface of the module cover is pressed by the airbag being inflated.
Some of driver-side airbag modules have a horn which is operated by pressing the module cover of the airbag module to activate a horn switch so as to cause the horn to sound. Such airbag modules with a horn switch are categorized into various types including a type in which the module cover and the retainer are movable together in the axial direction of a steering column so as to actuate the horn switch and a type in which the retainer is fixed to a steering wheel and only the module cover is movable.
Such airbag modules with a horn switch are further categorized into two types, one of which has three spoke-fitting portions formed in the module cover and the other one of which has four spoke-fitting portions formed in the module cover. In airbag modules having three spoke-fitting portions, the spoke-fitting portions are positioned on left and right portions and a lower portion inside a steering rim (the orientation is based on the steering wheel in a normal position in which the vehicle runs straight). The same holds true of the following description.). In airbag modules having four spoke-fitting portions, the spoke-fitting portions are positioned on upper left and upper right portions and lower left and lower right portions inside the steering rim as shown in FIG. 7.
In some airbag modules with a horn switch of the type having four spoke-fitting portions, switch units are arranged in the spoke-fitting portions, respectively. This arrangement increases the number of switch units for the horn switch and thus increases the cost. Therefore, some airbag modules of this type have three switch units in total, one of which is arranged at a middle portion between two spoke-fitting portions at the lower left and lower right sides (the lower left and lower right spoke-fitting portions) as shown in FIG. 7.
In this case, since the lower left and lower right spoke-fitting portions of the module cover are not backed up by any switch unit, the portions of the module cover should be pressed significantly deeply. That is, even after the horn switch is activated, the lower left or lower right portion of the module cover may be further deeply dented if the lower left or lower right portion of the module cover is further pressed. The driver may feel abnormality when the lower left or lower right portion of the module cover is deeply pressed and dented.